Research On Wavelet-based Robust Watermark

Digital watermarking is a new technique for information security. It embeds a special invisible mark into digital multimedia data, then carries out the functions such as information hiding, storing, copyright protection by tracking the use of the image by detecting the watermark. At present, watermarking technique has been a kind of effective means to multimedia copyright authentication and its integrity protection. This paper takes still images as example, firstly we give a brief introduction about the background, characteristics, types and applications of digital watermarking, and the attack of the digital watermarking is discussed in detail. Then brings chaotic encryption and wavelet transform theory into watermarking technique, and two watermarking algorithms are proposed. One is "An image adaptive blind watermarking algorithm based on HVS", and the other is "A zero-watermarking algorithm based on DWT". The main content about the algorithms are as follows. 1. An image adaptive blind watermarking algorithm based on HVS According to the background luminance and the texture mask characters of HVS the wavelet coefficients of carrier image is divided into different classes,and the classing result is based on the character of the image. Then after preprocessing the binary image watermark,with different embedding strength the watermark image is embedded by the rule of odd-even adjudging. This algorithm can extract the watermark without the original carrier image and the original watermark image. The experimental results show that the algorithm is invisible and robust against some image processing such as median filtering,JPEG compression,additive Gaussian noise,cropping attacks and so on. 2. A zero-watermarking algorithm based on DWT Zero-watermarking changes the traditional and common scheme that embeds watermarking into the original image, but draw out the watermarking from the image. This algorithm select the low frequency wavelet coefficients at random, and compare the coefficients to create the characteristic watermarking of the original image. The extraction takes the same method to get the characteristic watermarking of the tested image, then calculate the similarity and judged the copyright and the ownership of the tested image. The experimental results prove that the algorithm could make image distortion–free and be robust, simple, ease to use. Finally, it's the overall summarization of the paper and research expectations of the digital watermarking.